'Hair of His Head' in the Bible

All the days of the vow of his separation there shall no razor come upon his head: until the days be fulfilled, in which he separates himself unto the LORD, he shall be holy, and shall let the locks of the hair of his head grow.

However the hair of his head began to grow again after he was shaven.

And the people said unto Saul, Shall Jonathan die, who has worked this great salvation in Israel? God forbid: as the LORD lives, there shall not one hair of his head fall to the ground; for he has worked with God this day. So the people rescued Jonathan, so that he died not.

And when he cut the hair of his head, (for it was at every year's end that he cut it: because the hair was heavy on him, therefore he cut it:) he weighed the hair of his head at two hundred shekels after the king's weight.

I beheld till the thrones were set in place, and the Ancient of days did sit, whose garment was white as snow, and the hair of his head like the pure wool: his throne was like the fiery flame, and its wheels as burning fire.